1. Field of the Invention
The present invention relates to an internal pressure explosion-proof system, and some preferred embodiments relate to an internal pressure explosion-proof system preferably used as a robot system capable of detecting internal high pressure abnormality.
2. Description of Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
An internal pressure explosion-proof system equipped with an inactive-gas/air supplying portion and an inactive-gas/air discharging portion is known. See for example, Japanese Patent No. 2796482 (hereinafter referred to as “Patent Document 1”). According to this known design, an internal pressure of an internal pressure explosion-proof mechanism is monitored by a pressure detector, and a signal is sent to a protection monitoring device. The protection monitoring device is connected to a control apparatus of an internal pressure explosion-proof mechanism. If the internal pressure of the internal pressure explosion-proof mechanism in normal operation becomes lower than a predetermined value, the pressure detector detects the pressure drop and sends a signal to the protection monitoring device, and the control apparatus shuts down the power supply to the internal pressure explosion-proof mechanism upon receipt of the signal from the protection monitoring device.
On the other hand, in a purging work which should be done at the time of the startup of the internal pressure explosion-proof mechanism, the pressure detector sends a signal to the protection monitoring device if the internal pressure of the internal pressure explosion-proof mechanism becomes higher than a predetermined value. In this protection monitoring device, a timer is activated upon receipt of the signal and counts a time period during which the inactive-gas/air supplying portion can send inactive-gas/air of 5 times or more of the internal volume of the internal pressure explosion-proof mechanism. The abnormal detection of the internal pressure at the time of the normal operation and the method of the purging work are disclosed in the column of the prior art of Patent Document 1. In the invention disclosed by this patent, especially, for the purpose of simplifying the structure of the inactive-gas/air supplying portion and the inactive-gas/air discharging portion, it is configured to excite the electromagnetic valve for discharging the inactive-gas/air by the electric power sent to the internal pressure explosion-proof mechanism.
An internal pressure explosion-proof system equipped with an inactive-gas/air discharging portion is also known by Japanese Unexamined Laid-open Patent Publication No. 2003-62787 (hereinafter referred to as “Patent Document 2”). In this design, the inactive-gas/air discharging portion is provided with a main piping for releasing the inactive-gas/air discharged from the internal pressure explosion-proof mechanism, and the reserve piping formed in parallel with the main piping separately is formed. When the internal pressure explosion-proof mechanism becomes abnormally high in internal pressure for some reasons, the inactive-gas/air is released from a valve provided to the reserve piping to decrease the pressure of the internal pressure explosion-proof mechanism, to thereby to protect the inactive-gas/air discharging portion provided in the main piping.
The invention proposed by Patent Document 1 or the prior art technique disclosed in Patent Document 1 fail to disclose any means or solution to cope with the case in which the internal pressure explosion-proof mechanism is increased in internal pressure due to, e.g., troubles of the inactive-gas/air supplying portion, etc., not during the purging operation but during the normal operation.
Furthermore, in the invention disclosed by Patent Document 2, although the inactive-gas/air is released automatically when the internal pressure explosion-proof mechanism is increased in internal pressure and therefore the pressure of the reserve piping provided separately from the main piping becomes higher than a predetermined pressure, no means for warning a user the high-pressure abnormality is provided. In other words, in the invention disclosed by Patent document 2, a spare discharging piping is required apart from the main piping. Furthermore, the pressure in the internal pressure explosion-proof mechanism is decreased automatically, and since no means for notifying it of a user, the user cannot recognize the abnormality. In other words, no means for urging the maintenance and/or repair check was available, causing unnecessary releasing of the inactive-gas/air, which in turn becomes loads to the supplying source (e.g., compressor) of the inactive-gas/air.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.